A method for preserving cells and cell cultures (described in PCT Patent Application Publication No. WO/2012/109107, which is incorporated herein by reference) is known. The method was developed for reducing apoptosis in nucleated cells. The method entails holding nucleated cells in a container and adding a gas containing xenon to the container so that the pressure inside the container reaches between 0.5 to 4.0 atm. above ambient pressure; holding the container at between 0.5 to 4.0 atm. above ambient pressure for a period of time during which the temperature in the container is between 22° C. and 37° C.; lowering the temperature in the container to between 0.1° C. and 10° C. while maintaining the pressure of 0.5 to 4.0 atm. above ambient pressure and holding the container for a period of time; and reducing the pressure in the container to ambient pressure and increasing the temperature to 22° C. to 37° C. By performing these steps, the patent application discloses that the cells undergo less apoptosis than compared to cells that do not undergo such a treatment. The implementation of this method involves placing the cells in a container capable of withstanding up to 4.0 atm. of excess pressure in relation to atmospheric pressure. It is known that the standard platelet storage method involves storing platelets in a bag. The seams of such standard bags do not allow using this bag for implementing the above-indicated storage method. The creation of a bag capable of withstanding the above-mentioned high pressure would increase the bag cost, which is highly undesirable because these bags are single-use products. Also, this method is mainly intended for preserving nucleated cells, while the platelets are anucleated cells.
A method for preserving platelets described in US Patent Publication No. 2010/0009334, (which is incorporated herein by reference) is known. This method involves the preparation of platelet plasma out of the whole donated blood; keeping the platelet plasma in a gas medium containing from 65% to 100% of xenon under pressure for approximately 3.5 to 5 bars; subsequently cooling the platelet plasma down to a temperature of approximately 3° C. to 6° C.; and storing the platelet plasma range under the conditions of the above-indicated temperature and pressure of gas medium. US 2010/0009334 discloses that the method is implemented by placing the platelet concentrate in a gas-impermeable container into which a xenon-containing gas medium is fed under pressure. US 2010/0009334 also discloses the use of conventional gas-permeable bags intended for storing biological fluids (in particular, blood and blood components) and placing the gas-permeable bags in a gas-impermeable container into which a xenon-containing gas medium is fed under pressure. This method provides storage of platelets during a period of at least one week, which may not be long enough for some applications. Secondly, this method is best performed on small volumes of platelet concentrate—of the order of units of ml (i.e., placed into a vial, for example). It is believed that a sufficient amount of oxygen (required for maintaining metabolic processes in plasma) stays in a vial partially filled with such volume of platelet plasma. However, in actual practice, the platelets are required to be stored in standard bags with a volume of at least 200 ml, not in small vials. When the platelets are stored in bags, the amount of oxygen available for platelets may be insufficient for aerobic respiration, which can limit the duration of platelet plasma storage.
Another method for preserving platelets in the gas mixture (PCT Application No. PCT/US2012/057211 [WO 2013/049118] which is incorporated herein by reference) is known. According to this method, a platelet concentrate (obtained in advance from whole human blood) is kept in a gas mixture with xenon content from 79% to 95% and oxygen content from 5% to 21% under pressure from 3.5 to 5 bars at a temperature from 18° C. to 23° C., after which it is cooled down to a temperature from 3° C. to 6° C. and placed for storage under the conditions of the above-indicated composition and pressure of gas mixture and at above-indicated temperature. In this method, oxygen serves as a component of the gas mixture, in which the gas-permeable bag with platelet concentrate is stored. A design of the storage device for this method is not described.
A method and device for preserving blood or its components in a gas medium under pressure and system for the same (PCT Application No. PCT/US2012/043449 [WO 2012/177820] which is incorporated herein by reference) is known. According to this invention, blood or blood components are placed in a bag that is made of a xenon gas-permeable material. The bag is then placed into a hermetically-sealed cylindrical chamber into which xenon-containing gas (with a xenon content of at least 65%) is fed under pressure until the pressure in the chamber reaches the value approximately from 3.5 bars to 5 bars, after which the chamber is placed for storage at a temperature within the range from 3° C. to 6° C. Bags that are made of the gas-permeable material that are designed to allow xenon to pass through the bag are used for the implementation of this method. In this method, the xenon-containing gas (fed under pressure into the chamber) passes through the bag wall, after which blood or blood components in the bag are saturated with xenon. According to this method, the bag with the blood or blood components is placed in a cylindrical chamber and, during storage, the chamber is positioned vertically. The bag in the chamber is also positioned vertically, and the blood or blood components are not stirred in the course of storage. The absence of stirring and the vertical position of the bag in the course of storage can lead to a situation in which the platelets get deposited on a small area of the bag bottom, thus forming a dense deposit by the end of the storage period. Platelets in such a deposit can change their properties and a considerable part of the platelets can be activated and stick together. Platelets that are stuck to one another produce micro-aggregates which can result in the reduction in the number of free platelets, which in its turn, can lead to a decrease in platelet concentrate efficiency. Moreover, the sticking together of the platelets can lead to the formation of aggregates of quite considerable size, which could be detrimental for a recipient because, after transfusion, such aggregates may be capable of clotting the blood vessels, thus leading to disturbed blood circulation.
In view of the current state of the art, there is a need for a method for preserving platelet concentrate under pressure that does not lead to the formation of a dense deposit and aggregates of platelets.